In recent years, with the spreading of a broadband mobile communication service, high-speed and high-capacity communication is required and the third generation mobile communication system typified by a Wideband-Code Division Multiple Access (W-CDMA) system or a Long Term Evolution (LTE) system, which is the next-generation mobile communication system typified by a 3.5-generation mobile communication system, is used as a standard of the fourth generation communication system.
LTE is a communication standard defined by Third Generation Partnership Project (3GPP), in which a plurality of channel widths (1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, or, 20 MHz) are defined as a standard, Orthogonal Frequency Division Multiple Access (OFDMA) is used in the downlink, and Single Carrier-Frequency Division Multiple Access (SC-FDMA) is used in the uplink. LTE requires a communication speed, such as a downlink peak data rate of 150 Mbps or more and an uplink peak data rate of 50 Mbps or more (a frequency bandwidth is 20 MHz in both cases).
In addition, LTE-Advanced (hereinafter, referred to as “LTE-A”) which uses a broad band including a system band, which is the receivable bandwidth of LTE, in order to broaden the bandwidth and to increase the communication speed has been standardized.
LTE-A is characterized in that two techniques, that is, a technique for increasing the speed of a multiple-input multiple-output (MIMO) system, which is a spatial multiplexing technique, and a frequency bandwidth broadening technique (carrier aggregation), which bandwidth broadening means for aggregating LTE frequency blocks (a maximum channel bandwidth of 20 MHz) called component carriers, are adopted in order to flexibly broaden the frequency bandwidth while maintaining compatibility with LTE and each component carrier performs adaptive modulation and coding corresponding to a radio wave environment or a hybrid automatic repeat request (HARQ) to improve efficiency and the transmission speed (for example, see Non-patent Document 1).